This invention concerns an improvement to the devices for drawing fibers (in the form of roves or slivers) employed on spinning machines when making spun yarns of any type whatsoever (stub spun yarn, core spun yarn, self-twisted spun yarn, . . . ). It deals more particularly with an improvement made to the drawing devices incorporating so-called "pendulous arms", such as for example those marketed by the firm SKF, well known to the man skilled in the art and described in particular in French Patents published under Nos. 1 343 069, 2 081 694 and 2 081 886.
Such pendulous arms which are shown schematically in accompanying FIGS. 1 and 2, in side view in work position in FIG. 1 and in disconnected view in FIG. 2, are essentially constituted by an assembly comprising, mounted on the support frame 1 of the machine, on the one hand, a series of splined shafts 2 extending over the whole length of the machine and common to all the work positions, said shafts being driven in rotation, their number and spaced apart relationship being a function of the materials to be treated and the drawing rates to be given and, on the other hand, presser elements constituted by rollers 3, mounted on a supporting, so-called "pendulous" arm 4. As seen in particular in the French Patents mentioned hereinabove, the pressure exerted by the rollers 3 on the splined shafts 2 is generally obtained by means of helical springs working in compression. The pressure is adjustable on each roller 3 individually. Other means such as pneumatic means may possibly be used to ensure this pressure. The arm 4 is mounted about a pivot 5 on a support 6 itself fixed on a bar 7 extending over the whole length of the loom. The abutment of the presser rollers against the splined shafts 2 is obtained by means of a lever 8 on which the operator acts in order either to place the assembly in work position (FIG. 1) or, on the contrary, to separate the presser rollers 3 when an operation must be effected on the drawing system. In general, disconnection is effected, after the pressure is released, in the order: feed zone (A) towards outlet zone (B) and, at closure, the order is reversed. The structure and operation of such drawing devices are clearly shown in French Pat. No. 2 081 886 and will therefore not be described in detail.
Accompanying FIGS. 1 and 2 clearly show that, when it is desired to open the drawing system, for example upon a restart, there is a very large clearance between the splined shafts and the presser rollers which, in certain cases, may be detrimental when it is desired to render such operations automatic.
In addition to this drawback, upon disconnection, windings of fibers may be formed around the splined shafts and, furthermore, upon restart, there is the problem of refining of the feed rove, which problem is all the greater as the present tendency is to make very high drawing rates and therefore to use feed roves of high count.
An improvement to such pendulous drawing systems has now been found, and this forms the subject matter of the present invention, which overcomes these drawbacks and which ensures in particular disconnection of the drawing system without acting on the pressure exerted on the presser rollers and without pivoting of the pendulous arm, whilst maintaining the rove in its state of drawing, this facilitating the operations of restart, particularly in the case of the feed material being constituted by a sliver of fibers of high count.